The present invention relates to an electroacoustical telephone adapter, and more particularly, relates to an electroacoustical telephone adapter which greatly enhances the quality of telephone communications in a hands-free telephone.
The present invention substantially reduces the "echo" effect of the frequently observed effect that the speaker seems to be "talking in a well or tank" when using the hands-free telephone equipment presently on the market. It is believed that this "echo" effect is caused in conventional hands-free telephones by the use of non-directional microphones which pick up multi-path reflections with their attendant phase reinforcements and cancellations. The present invention also provides advantages, inter alia, in the area of switching between the transmit and receive modes of operation.
Telephone adapters for using telephones without the requirement of holding a handset are known in the art. For example, U.S. Pat. No. 3,887,771-Abram N. Spanel discloses a telephone adapter which may be used to enhance the quality and ease of communication by telephone over the then existing prior art. The aforementioned patent of Abram N. Spanel enhances the quality of communication by use of a re-entrant horn which provides acoustic amplification of sounds to be transmitted over the telephone system. The acoustically amplified sounds are directly coupled to the mouthpiece of the handset of a conventional telephone. The present invention provides improvements over the teachings of the aforementioned patent of Abram N. Spanel by combining the directional characteristics of an acoustical horn with switched electronic amplification.
Both the aforesaid patent of Abram N. Spanel and U.S. Pat. No. 2,987,575-Chalfin teach the use of electronic amplification of received sound. In both of the aforesaid patents, the earphone is inductively coupled to an amplifier circuit which amplifies a signal which is then applied to speaker means. The present invention provides improved speech transmission by the use of the combination of a re-entrant horn and electrical amplification circuitry. The re-entrant horn provides directivity of sound reception. The electrical amplification circuitry receives a signal from a microphone mounted at the tail or output portion of the horn, amplifies and frequency shapes the electrical signal. The amplified and frequency shaped electrical signal is then reconverted to sound by a transducer. The transducer is mounted to enable coupling of the sound to the mouthpiece of the handset of a telephone.